This paper describes the dependence of the dislocation density reduction effect on the employing position of either thermal cyclic annealing (TCA) or InGaAs-GaAs strained-layer superlattice (SLS) in GaAs-on-Si grown by metalorganic chemical vapor deposition (MOCVD). The dislocation density is reduced to one twenty-fifth of that in as-grown sample by the TCA as the position of TCA becomes farther than about 1.5 µm from the Si surface. The dislocation density is additionally reduced to one third by the SLS as the position of SLS becomes farther than about 2.0 µm. As a result, the dislocation density is reduced to 1.5 × 106 cm-2 by the combined use of TCA and SLS. The dislocation density reduction effect of TCA is determined mainly by the degree of residual stress. That effect of SLS is determined mainly by the degree of additional stress generated by SLS.

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The origin of the thermal instability of the AlInAs/GaInAs system is identified and a novel method to recover the thermal degradation is also demonstrated. The thermal diffusion of fluorine into the Si-doped AlInAs layer is found to be the main cause of the electrical deterioration of this system. This finding has led to a method to recover the thermal degradation by purging the fluorine off using the reannealing in the ultrahigh-vacuum condition. This method is now potentially becoming a good candidate as a tip for the AlInAs/GaInAs devices fabrication including laser diode and high electron mobility transistor.

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This paper describes the study of crack propagation and mechanical fracture in GaAs-on-Si, which are closely related with the residual stress. The crack propagation is often observed as the GaAs thickness exceeds about 3 µm, and the upper limit of the number of cracks increases linearly as the GaAs thickness increases. The cracks propagate from the surface defects, where stress ten times larger than the original residual thermal stress in GaAs-on-Si exists. The mechanical fracture strength (ζ) of the GaAs-on-Si wafer decreases as the GaAs thickness increases, and becomes equal to that of the bulk GaAs at the thickness of about 3 µm due to the concentrated stress near the cracks. The back coating of SiO2 is effective for stress relaxation, and the preliminary result of about 3×108 dyn/cm2 of stress relaxation is obtained.